Production of Synthetic Lightweight Aggregates from Industrial Sludge

Area of Science:

• Materials Science
• Environmental Engineering
• Waste Management

Background:

• Industrial sludge generation is increasing globally, posing significant waste management challenges.
• Incineration of industrial sludge, common in Taiwan, leads to pollution and prevents material reuse.
• Developing sustainable methods for industrial sludge treatment and reuse is an environmental priority.

Purpose of the Study:

• To investigate the feasibility of producing lightweight aggregates from a mixture of water treatment sludge (WTS) and industrial sludge.
• To evaluate the physical and chemical properties of the resulting lightweight aggregates.
• To assess the potential for energy saving and carbon reduction through this reuse method.

Main Methods:

• Lightweight aggregates were prepared by mixing WTS with varying percentages (7.5%, 15.0%, 22.5%) of industrial sludge.
• Chemical composition was analyzed to ensure suitability for expansion, with ternary phase diagrams used for evaluation.
• Sintering experiments were conducted in two stages to determine optimal temperatures and preheating times (5, 10, 15 min).

Main Results:

• Lightweight aggregates sintered successfully with up to 22.5% industrial sludge, meeting density (0.5–1.4 g/cm³) and water absorption (<21%) specifications.
• Increased preheating time enhanced particle density but reduced water absorption due to gas escape, hindering expansion.
• Industrial sludge's loss on ignition (50–70%) created pores/cracks, indicating efficient energy conversion during sintering.

Conclusions:

• Industrial sludge can be effectively reused as a secondary ingredient in lightweight aggregate production from WTS.
• This method provides a viable alternative to incineration, reducing environmental pollution and promoting material circularity.
• Utilizing industrial sludge in lightweight aggregates leads to energy savings and carbon emission reductions during the sintering process.